OK, well you were half right in your question. In order to play on XBox live you will need either the wireless network adapter or run an Ethernet cable from your 360 to your home router. Simply having the hard drive will not allow you to play on XBox live.
Xbox Wireless Network Adapter MN740
The adapter connects you to Xbox Live but only if you have a wireless network and if you have a Xbox Live subscription.
It allows you to connect to xbox live on a wireless network
I am not going to say it is impossible for a different adapter to work, just unlikely . The Xbox 360 Wireless Network Adapter was made specifically for that purpose, so it is unlikely that a normal adapter will work if attached to the Xbox as they most likely will not be compatible.
no
Don't no
Google the Xbox 360 Wireless Network Adapter.
The newer models (with the internal hard drive and whatnot) do, but for older ones you'll have to buy an adapter separately.
The Xbox 360 Wireless adapter uses standard 802.11b, 802.11g, and 802.11a connections. If your Mac has an AirPort wireless network card it will be able to connect to the Xbox network.
To hook up an XBox 360, one would need the XBox 360 Wireless Network Adapter. This specific adapter is easy to install, is compatible with Windows Vista Media Center, is compatible with 2.4 Ghz and 5 Ghz wireless networks and allows wireless play on Xbox LIVE.
Yes, it is possible to use a laptop as a wireless bridge for xbox live.
Yes